1. Field of Invention
The invention relates to a dielectric antenna having an at least partially dielectric body and an electrically conductive sheath, wherein the dielectric body can be struck with electromagnetic radiation on a supply section and the electromagnetic radiation can at least partially be emitted from the dielectric body via a lens-shaped radiation section. The conductive sheath essentially surrounds the dielectric body from the supply section to the radiation section and a supply opening is provided in the conductive sheath in the area of the supply section and a radiation opening is provided in the conductive sheath in the area of the radiation section.
2. Description of Related Art
Dielectric antennae are known from different fields of engineering in very different configurations. However, dielectric antennae have in common that dielectric materials are used for guiding and emitting electromagnetic waves, in particular, such dielectric materials that are particularly low-loss. It is known to use, e.g., TEFLON® or polypropylene or other dielectrics having a low permittivity as a dielectric material for the dielectric body.
Dielectric antennae are often used, e.g., for fill level measurement in industrial process measurement engineering. In such—but also in other—fields of use, it is of particular advantage for the antennae to have a main emission direction that is as narrow as possible, and at the same time, a configuration that is as compact as possible. However, these requirements are contradictory in terms of constructive measures, which normally have to be used for technical implementation. A narrow directional characteristic in the main emission direction can, as is generally known, first be achieved using a large aperture—i.e., opening area—of the radiation section. So that the aperture is also used in the sense of a narrow main emission direction, the electromagnetic radiation emitted from the emission area of the lens has an even as possible phase front, wherein such an even phase front is more easily implemented with an increasing length of the antenna, which conflicts with the desired compact configuration.
In addition to the difficult implementation of a narrow main radiation direction and simultaneous compact configuration, known dielectric antennae have a further disadvantage, which is associated with the mutual arrangement of electromagnetic supply element—waveguide—and the dielectric body or, respectively, lens formed of dielectric material.
In the configuration of antennae, in which the electromagnetic supply element and the dielectric body have direct contact with one another, the dielectric body is enclosed by at least parts of the electromagnetic supply element, namely the conductive sheath. When it is being discussed that the conductive sheath “essentially” encloses the dielectric body from the supply section to the radiation section, then it is meant that it is not compulsory that the conductive sheath serving as a boundary of the electromagnetic radiation extends exactly to the edge of the radiation section, since possibly due to the chosen geometry of the sheath, it is not possible that electromagnetic radiation struck in the supply section reaches this end area of the dielectric body. It is also meant that it is not compulsory that the sheath be a “closed” sheath in an optical sense, since, depending on the chosen electromagnetic radiation, the desired effect of reflection is also achieved by an amply closed, conductive grate.
In other configurations, an electromagnetic supply element—waveguide—and the dielectric body or, respectively, the lens made of dielectric material, are arranged at a distance from one another, so that a space results between the supply element and the dielectric body.
Both of the variations mentioned above have the disadvantage that a configuration suitable also, for example, for hygienic purposes can only be poorly implemented. Aside from the already very challenging structural implementation of an antenna having a dielectric body at least partially enclosed by the conductive sheath, this configuration has the additional disadvantage that the conductive sheath and the dielectric body extend together up to a far preceding area of the antenna and are comparably exposed and, thus, are at risk for contamination. In the antenna construction with the space between the electromagnetic supply element and the dielectric body, there is always the risk of contamination of the antenna surfaces that are facing the space; furthermore, excess and negative pressure applications could be a problem due to the existing space.
Furthermore, such dielectric antennae having a tapered form opening in the direction of radiation and having a tapered conductive sheath have been shown to be disadvantageous in that the production effort for such angled—but not right-angled—constructions is comparably high, so that there is interest in finding simpler and more inexpensive ways to produce antennae configurations, having at least comparable radiation characteristics to those antennae known from the prior art.